The benefit of dual mobility cup (DMC) for primary total hip arthroplasties (THA) is still controversial. This study aimed to compare 1) the complications rate, 2) the revisions rate, 3) the survival rate after monobloc DMC compared to large femoral heads (LFH) in primary THA.

Between 2010 and 2019, 2,075 primary THA using cementless DMC or LFH were included. Indications for DMC were patients older than 70 years old or with high risk of dislocation. Every other patient received a LFH. Exclusion criteria were cemented implants, femoral neck fracture, a follow-up of less than one year. 1,940 THA were analyzed: 1,149 DMC (59.2%), 791 LFH (40.8%). The mean age was 73 ±9.2 years old in DMC group and 57 ±12 in LFH group. The complications and the revisions have been assessed retrospectively.

The mean follow-up was 41.9 months ±14 [12–134]. There were significantly fewer dislocations in DMC group (n=2; 0.17%) compared to LFH group (n=8; 1%) (p=0.019). The femoral head size had no impact on the dislocations rate in LFH group (p=0.70). The overall complication rate in DMC (n=59; 5.1%) and LFH (n=53; 6.7%) were not statistically different (p=0.21). No specific complication was attributed to the DMC. In DMC group, 18 THA (1.6%) were revised versus 15 THA in LFH group (1.9%) (p= 0.71). There was no statistical difference for any cause of revisions in both groups. The cup aseptic revision-free survival rates at 5 years were 98% in DMC group and 97.3% in LFH group (p=0.78).

Monobloc DMC had a lower risk of dislocation in a high-risk population than LFH in a low-risk population at the mid-term follow-up. There was no significant risk of specific complications or revisions for DMC in a large cohort. Monobloc DMC can be safely used in a selected high-risk population.

Aims

The use of high tibial osteotomy (HTO) to delay total knee arthroplasty (TKA) in young patients with osteoarthritis (OA) and constitutional deformity remains debated. The aim of this study was to compare the long-term outcomes of TKA after HTO compared to TKA without HTO, using the time from the index OA surgery as reference (HTO for the study group, TKA for the control group).

Introduction and Objective

In recent studies, robotic-assisted surgical techniques for unicompartmental knee arthroplasty (UKA) have demonstrated superior implant positioning and limb alignment compared to a conventional technique. However, the impact of the robotic-assisted technique on clinical and functional outcomes is less clear. The aim of this study was to compare the gait parameters of UKA performed with conventional and image-free robotic-assisted techniques.

Introduction

In prosthetic knee surgery, the axis of the lower limb is often determined only by static radiographic analysis. However, it is relevant to determine if this axis varies during walking, as this may alter the stresses on the implants. The aim of this study was to determine whether pre-operative measurement of the mechanical femorotibial axis (mFTA) varies between static and dynamic analysis in isolated medial femorotibial osteoarthritis.

Introduction

Increasingly young and active patients are concerned about revision arthroplasty forcing the manufacturers to think about revision prostheses that fit to this population while meeting the indications and fitting with bone losses and ligament deficiencies. One of those industrials claims that its system allows the surgeon to rise the constraint from a posterior stabilized (PS) prostheses to a semi-constraint total stabilized (TS) prostheses without modifying the gait pattern thanks to a similar single radius design. The aim of the study was to compare gait parameters in patients receiving either PS or TS knee prostheses.

Introduction:

High tibial osteotomy (HTO) is a common treatment for medial compartment arthritis of the knee in younger, more active patients. The HTO shifts load away from the degenerative medial compartment and into the lateral compartment. This change can be accomplished with either a lateral closing or a medial opening wedge HTO. An HTO also potentially affects leg length. Mathematical models predict that the osteotomy type (opening versus closing) and the magnitude of the correction determine the change in leg length, but no in vivo studies have been published. The purpose of this study is to quantify and compare leg length change following opening and closing wedge HTO.

Background:

Appropriate positioning of total knee arthroplasty (TKA) components is a key concern of surgeons. Post-operative varus alignment has been associated with poorer clinical outcome scores and increased failure rates. However, obtaining neutral alignment can be challenging in cases with significant pre-operative varus deformity

For many patients, UKA is a good alternative to total knee arthroplasty (TKA) or high tibial osteotomy (HTO). Strong evidence that gender influences outcomes following UKA could alter UKA selection criteria. No prior series has been specifically designed and matched to compare outcomes based on gender. The purpose of this study was to elucidate the effect of gender on the clinical outcome of UKA while controlling for other variables that may affect outcome.

Between 1988 and 2006, 257 UKA's were carried out in our department. We studied two groups of 40 patients of each gender, matched by pre-operative clinical and radiological presentation, and with post-operative follow up of at least 2 years. The mean age at operation was 71 years and the mean follow-up was 5.9 years. In both groups, IKS score improved significantly.

When comparing the male and female groups post-operatively, no significant differences were found between IKS knee or function scores, limb alignment, or the incidence of radiolucent lines. No difference was found between groups in terms of range of motion or radiologic progression of arthritis. Both tibial (p<0.001) and femoral (p<0.001) component sizes were significantly larger in the male group than the female group. For males, the size of both the femoral (r2=0.12, p=0.033) and tibial (r2=0.29, p=0.0005) components correlated with patient height. For females, the size of neither the femoral (r2=0.000082, p=0.96) nor tibial (r2=0.0065, p=0.63) components correlated with patient height.

The key finding in this study is that when patients are selected for UKA according to specific selection criteria (including avoiding performance of UKA in younger patients and patients over 85 kg), gender is not a predictor of outcome based on IKS scores. When using these selection criteria, gender should not be considered when determining whether to perform a UKA.

To our knowledge in medial unicompartmental knee arthroplasty (UKA) no study has specifically assessed the difference in outcome between matched gender groups. Previous unmatched gender studies have indicated more favourable results for women.

Introduction

It is documented in the literature the very good results of lateral unicompartmental knee arthroplasty (UKA) when the standard accepted indications are followed. In our experience these indications can be extended to include post-traumatic osteoarthritis (OA) with malunion secondary to tibial plateau fracture. We report our results concerning 15 UKAs in these particular situations.

Purpose of the study: The purpose of this retrospective multicentric analysis was to study the functional and radiological outcomes at more than 20 years of 89 arthroscopic lateral menisectomy procedures performed on stable knees.

Materialandmethod:The series included 89 arthroscopic lateral meniscectomies performed on knee with intact anterior cruciate ligaments (ACL). Mean follow-up was 22±3 years; 56 male, mean BMI 25±4, mean age at meniscectomy 35 years, mean age at last follow-up 57 years. Most of the injuries were vertical (41%), complex (22%) and radial (20%) lesions. The middle segment was involved in 79%. The meniscectomy removed more than one-third of the meniscus in 67%. All patients were reviewed by an independent operator for subjective assessment KOOS (100% normal) and IKDC, and for objective clinical and radiological measurements (IKDC). P< 0.05 was considered statistically significant. There was no independent control group.

Results: Revisions were performed for 16% of the knees. Intense or moderate activity was maintained by all patients. The subjective IKDC score was 71.1±23, comparable with an age and gender matched population. The mean KOOS score was 82% for pain, 80% for symptoms, 85% for daily activities, 64% for sports, and 69% for quality of life. The rate of of osteoarthritis was 56%, and 44% of patients had a difference between the two knees for osteoarthritis. The incidence of osteoarthritis was 53% and shift to valgus on the arthritic side was significantly associated with osteoarthritis, while the opposite side was well aligned. The knee was pain free in 27% of patients. Significant factors for good prognosis were age less than 38 years at first operation, moderate BMI, and minimal cartilage damage (grade 0 or 1).

Conclusion: After the first postoperative year after arthroscopic lateral meniscectomy on a stable knee, the results remain stable and satisfactory for more than 22 years. Nevertheless, patients aged over 40 with a high BMI and cartilage damage at the time of the first operation have a less encouraging prognosis.

Purpose of the study: Transposition of the anterior tibial tuberosisty (ATT) is often performed during the treatment of periodic dislocation of the patella. The purpose of this retrospective study was to evaluate the rate of medial femorotibial osteoarthritis and medial patellofemoral osteoarthritis after ATT transfer.

Material and method: We reviewed 129 knees in 106 patients who underwent surgery from 1988 to 2004. The patients were reviewed at mean 9 years follow-up, minimum 2 years. Three groups were defined:

isolated descent (n=15),

The degree of the medial shift and the descent depended on the distance from the tibial tuberosity to the trochlear notch and the Caton-Deschamps index measured preoperatively. Patients who underwent surgery for chronic anterior laxity and/or meniscal lesions were excluded (n=3). All patients were free of osteoarthritis before surgery. A complete radiographic series was available for 102 knees. Unilateral periodic dislocation of the patella was present in 60 patients whose knee x-rays were obtained bilaterally.

Results: All patients in group 2 were free of osteoarthritis. In group 2, the rate of medial femorotibial osteoarthritis was 10.5%; the rate of medial patellofemoral osteoarthritis was 21%. In group 3, the rate of medial femorotibial osteoarthritis was 7% and that of medial patellofemoral osteoarthritis 14%. For patients with unilateral periodic patellar dislocation, only the operated knees exhibited medial patellofemoral osteoarthritis (12%). The rate of medial patellofemoral osteoarthritis was significantly greater for knees with a medial shift of the ATT. The rate of medial femorotibial osteoarthritis was 6.8% for knees with medial shift versus 8.3% for the index knees. There was no significant difference between the medial shift knees and the index knees for medial femorotibial osteoarthritis.

Discussion: Biomechanical studies have shown increased stress forces on the medial compartment after medial shift of the ATT. However, these studies were performed with normal knees free of the morphological anomalies generally present in knees exhibiting periodic patellar dislocation (abnormally high tibial tuberosity femoral notch distance, trochlear dysplasia. In our series, regarding the rate of medial femorotibial osteoarthritis, there was no significant difference between the knees which underwent a medial shift of the ATT and healthy knees. Consequently, medial shift of the ATT should be avoided when unnecessary; the morphology of the trochlea (depth, morphology of the medial component) can induce increased medial stress on the patellofemoral joint.

Purpose of the study: The purpose of this study was to report the results observed in a consecutive series of 54 lateral unicompartmental knee prostheses with minimum five years follow-up.

Material and methods: One hundred forty-four unicompartmental cemented HLS resurfacing prostheses were implanted with a chromium-cobalt femoral element and an all polyethylene polyethylene element. Among these consecutive implantations performed from 1998 to 2003 in accordance with indications established in 1988, 54 were lateral unicompartmental knee prostheses (37.5%) implanted in 10 men and 44 women. Mean age was 68.5 years (range 25–88). A lateral approach was used for the first six implants in this series. One patient was lost to follow-up, five died and one underwent revision for a total prosthesis. Forty-seven patients were reviewed with mean 100.9 months follow-up (64–159). Clinical data were analysed with the IKS criteria and all patients had a complete radiographic work-up before surgery and at last follow-up.

Results: In this series 96.3% of patients (n=52) were satisfied or very satisfied. Mean flexion was 133 (110–150). The mean knee score was 81.1 (25–100). Mean residual alignment was 2° valgus. A lucency was noted in 13.2% of knees, but remained stable. There was one failure requiring revision for a total prosthesis (loosening of the tibial component). The Kaplan-Meier survival was 98.1% at ten years. Three patients exhibited wear of the medial femorotibial compartment and had a medial unicompartmental implant. The overall survival (rein-tervention irrespective of reason) was 91.1%.

Discussion: Outcomes were very satisfactory, globally similar to recent series in the literature. Reliable sustainable outcomes with lateral unicompartmental implants have led us to widen our indications (moderate overweight, younger patients).

Recently in Europe, Unicompartmental Knee Arthroplasty (UKA) has regained interest in the orthopedic community; however, based on various reports, results concerning UKA for isolated lateral compartment arthritis seemed to be not as good as for medial side. In 1988 our department started using Unicondylar Knee Pros-thesis with a fixed all polyethylene bearing tibial component and resurfacing of the distal femoral condyle. The aim of this study is to report on our personal experience using this type of implant for lateral osteoarthritis with a long follow-up period.

Between January 1988 and October 2003, we performed 54 lateral UKAs (52 patients) and all were implanted for lateral osteoarthritis (3 cases of which were posttraumatic). 52 knees in 50 patients were available after a minimum duration of follow-up of five years (96.3 %). The mean age of the patients at the time of the index procedure was 72.2±1.5 years. The mean duration of follow-up was 100.9 months (range 64 – 189 months).

At follow up, 4 underwent a second surgery: one conversion to TKA for tibial tray loosening at 2 years and 3 revisions for UKA in the medial compartment. No revision surgery was necessary for wear of either of the two components, nor for infection. The mean IKS knee score was 94.9 points, with mean range of motion 132.6° (range, 115–150) and a mean IKS function score totaling 81.8 points. The average femorotibial alignment was 1.8° (range −6° to 12°). Radiolucent lines in relation to the tibial component were appreciated in 6 knees and to the femoral component in 1 knee. Implant survival was 98.08% at ten years.

The UKA with a fixed bearing tibial component and a femoral resurfacing implant is a reliable option for management of isolated lateral knee osteoarthritis. It offers excellent medium-term results for both functional level and implant survival which even currently enable us to widen our selection criteria to include younger patients or those associated with starting patellofemoral osteoarthritis.

Introduction: Increasing popularity of unicompartmental knee arthroplasty (UKA) brings greater relevance for possibilities and outcome of revision surgery. UKA is less aggressive, allows earlier rehabilitation and better kinematics comparing to total knee arthroplasty (TKA). It is tempting to apply such advantages in cases with secondary degenerative changes in the opposite compartment after an UKA with satisfactory results by implanting a contralateral UKA (BiUni). Absence of loosening or wear with overcorrection under 5° after first prosthesis and patient selection criteria for UKA in the opposite compartment are required.

Material and Methods: From June 2004 to January 2007 six BiUni were done, out of ten secondary surgeries following UKA (six BiUni, three arthroscopies and one TKA conversion). Four consisted in external UKA after medial and two others the opposite. All have been submitted to prospective radiologic and clinical evaluation (International Knee Society Score-IKSS) with 25.5 months mean follow-up (12 to 42).

Results: Identified causes for secondary arthritic changes included: “hypercorrection” (n=3), partial lateral meniscectomy (n=2) and femoral condyle osteonecrosis (n=1). Before BiUni the mean IKSS knee was 62.5 (60 to 70) and IKSS function 65.0 (60 to 70). At latest revision, mean IKSS knee was 92.5 (80 to 100) and function 87.5 (70 to 100). No radiologic signs of wear or migration were noticed.

Discussion: There are only few papers in literature regarding this concept. BiUni is not about revising failed UKA neither is a bycondilar knee arthroplasty. These results encourage further evaluation about possible long-term advantages for strictly selected cases particularly those at higher risk for TKA.

Introduction: Lateral meniscectomies lead to degenerative arthritis and therefore meniscus transplantation has been considered. In literature, this procedure appears to have good clinical results. The aim of this study was to evaluate our clinical results at mid-term follow-up and to correlate these results to the morphology and position of the transplanted meniscus.

Material and methods: Twenty-eight patients operated in 4 surgical centers, were retrospectively reviewed following lateral meniscal allograft transplantation. The mean age of the patients was 34 years (range, 18 to 50 years). Before surgery, all these patients suffered of permanent lateral femorotibial pain without radiological knee arthritis. The knees were all stable or stabilized, without axial malalignment of the lower limbs or corrected by a concomitant high tibial osteotomy. Arthroscopic procedure was performed for 9 patients and arthrotomy for 19 patients. Different techniques of fixation of the transplant were used, with or without bone plugs. The associated procedures were 2 ACL reconstruction, 3 high tibial varus osteotomies, and 1 mosaicplasty. The IKDC score were used for the analysis of the functional results. An arthroTDM or an arthro MRI was used to analyse the morphology and position of the transplanted meniscus.

Results: The mean follow-up was 35 months (range, 12 months to 6 years). The mean post-operative subjective IKDC score was 65.5 points (range, 19.5 to 89 points). There were 2 failures associated with a fast arthritic evolution and 2 functional bad results. The others 24 patients (85%) were satisfied or very satisfied, with a real improvement of the pain and the function. Seventeen patients (60%) have started again a sportive activity superior than the one pre-operating. At the last follow-up, all transplanted meniscus have healed, but the morphology and position of the transplanted meniscus was not always normal with absence of the middle segment in 3 cases; its extrusion in 9 cases, a posterior segment shortened or partially hurt in 5 cases and its absence in 3 cases. Better results were associated with good meniscus positioning and morphology.

Discussion: Our works confirm that lateral meniscal allograft is a therapeutic option with favourable results in terms of pain reduction and functional improvement in the medium term for symptomatic patients after lateral meniscectomy. Our results are comparable with those of the literature. The allograft is technically reliable, reproducible notably for the methods of fixation. A long term follow-up is necessary to evaluate the benefit of these grafts on the protection of the cartilage.

Purpose of the study: Posterior shoulder instability is a rare condition. Several surgical treatments have been proposed.

Material and methods: This was a retrospective series of 21 posterior bone block procedures performed between 1984 and 2001 and analyzed with mean follow-up of six years. Fifteen patients (n=16) had experienced one or more episodes of posterior dislocation. Thirteen patients were athletes and five had traumatic subluxation with chronic posterior instability. Voluntary recurrent dislocations were not observed in these patients. Male gender predominated (n=19 men, 1 woman). Mean age at surgery was 24.8 years (range 17–40). The dominant side was involved in 12 patients (57%). The Constant and Duplay scores were noted as were the pre- and postoperative x-ray findings. There were ten glenoid fractures, two glenoid impactions, ten anterior humeral notches. Mean retroversion, measured on the scans (n=17) was 9.6° (range 0–21°).

Results: All patients (n=20) were satisfied or very satisfied. At last follow-up, the mean Constant score was 93.3 (range 80–103) and the mean Duplay score (n=21) 85.6 (40–100); 68.2% of patients (n=15) resumed sports activities at the same level. Failure was noted in three patients, one with recurrent posterior dislocation and two with major apprehension. For two patients, glenohumeral osteoarthritis developed postoperatively.

Discussion: Most of the series in the literature have reported results for patients with recurrent posterior subluxations and not for traumatic posterior dislocation, the much more uncommon entity presented here. The rate of bony lesions was high in our series compared with former series in the literature. These results can be explained by two facts. The first that this was a group of recurrent posterior dislocations and second that the analysis of the osteoarticular lesions was made on plain x-rays and/or CT scans. For the two cases of glenohumeral osteoarthritis which developed postoperatively, the position of the bone block does not appear to be involved.

Conclusion: The posterior bone block remains the treatment of choice for recurrent posterior dislocation. The risk of developing osteoarthritis appears to be low but a longer follow-up would be necessary for confirmation.

Purpose of the study: Cysts are rarely identified in the anterior cruciate ligament; the pathogenic mechanisms involved are poorly understood. We investigated the anatomic and clinical presentation.

Material and methods: This retrospective analysis included 24 patients, seven women and seventeen men managed in a single center from 1998 to 2004. Mean patient age was 45 years (range 25–74 years). All patients complained of pain. A preoperative MRI was available for all patients. Mean follow-up was 25 months (range 6–48 months). Arthroscopic procedures were used for 17 patients and the IKDC subjective score was determined preoperatively in all. Radioguided (US or CT) puncture was performed for seven patients associated with corticosteroid injections.

Results: On the MRI, there were 16 infiltrating cysts and eight cystic formations. Surgical treatment (n=17) was performed for 13 infiltrative cysts and for four cystic formations. There were two cases of recurrence. Outcome was poor after puncture (two puncture failures, three recurrences and one vascular complication).

Discussion: Two forms of cysts of the ACL can be demonstrated by MRI. The clinical presentation may not be different but the therapeutic management should be. The cystic formation is an indication for puncture, with arthroscopic treatment in the event of failure. For infiltrating cysts, complete resection of the cyst during an arthroscopic procedure is indicated, sometimes associated with resection of the ACL. Puncture yields poor results.

Purpose of the study: The purpose of this retrospective study was to analyze clinical datao n pigmented villon-odular synovitis (PVSN) of the knee as well as outcome after treatment in order to define the diagnostic stages, the surgical treatment, and follow-up modalities for this rare benign proliferative disease of the synovial which predominantly affects the knee joint.

Material and methods: Between 1996 and 2004, 28 patients were managed in our department, 13 men and 15 women, diffuse PVNS in 20 and localized PVNS in 8. IN the localized forms, symptoms were similar to those observed in knees with intra-articular foreign bodies or a meniscal lesion (75%) was present for 14 months on average at the first consultation. Mean age at onset of therapeutic management was 40 years (range 20–62). Localized arthroscopic or open resection was performed. For the diffuse forms, symptoms had been present for 15 months on average at the first consultation. Patients sought medical care because of spontaneous hemarthrosis or diffuse knee pain with no specific signs. Mean age at onset of therapeutic management was 38 years (range 15–59). Bony lesions were observed in 20%. Synoviorthesis or surgical synovectomy were performed. Mean follow-up was 97 months (range 12–309). Outcome was analyzed separately for the localized and diffuse forms.

Results: For the localized PVNS, there were no complications after surgical treatment but the relapse rate reached 12.5%. For diffuse PVNS, the cumulative rate of relapse was 50%, recurrence being noted on average 37 months after treatment. A stiff joint developed in 14% after open synovectomy. Surgical treatment was necessary in four cases (total arthroplasty in three) seen late after development of bony lesions; the clinical outcome was good with good gain in flexion.

Discussion: MRI is essential for the topographic diagnosis and to guide surgery. For diffuse PVNS seen at an advanced stage or after several recurrences, adjuvant synoviorthesis can be useful 4 to 8 months after surgery.

Conclusion: Appropriate treatment of PVNS of the knee depends on the presentation but usually involves a surgical procedure. The risk of recurrence for diffuse PVNS warrants annual MRI for four years.

Purpose: One of the difficult problems during the implantation of a total knee prosthesis is the presence of preoperative stiffness or permanent flexion.The later is a sign of advanced stage degradation due to osteoarthritis or rheumatoid arthritis. We wanted to describe the technical specificities of a total knee arthroplasty (TKA) implanted in patients with permanent flexion and to analyse long-term outcome.

Material and methods: We studied a series of 826 posterior stabilised TKA (HLS) implanted since 1988 (followed prospectively since 1995). We defined three groups of patients according to the degree of preoperative flexion: group I (0°–10°), group II (11°–20°), and group III (> 20°). We evaluated the operative technique itself, then analysed long-term clinical and radiological outcome using the IKS scores.

Results: There was no significant difference in the objective or subjective clinical or radiological outcomes in the first two groups (I and II). Outcome appeared to be less satisfactory in patients with permanent flexion greater than 20°, but the statistical analysis was not feasible.

Discussion: This study enabled us to describe the specific preoperative planning and the operative steps necessary for patients with permanent flexion preoperatively. The results of our series do no enable distinction between the long-term results in patients with < 20° flexion. Beyond this level, techniques for bony or ligamentary release influence the results which are less satisfactory. Posterior stabilisation enables release of the posterior cruciate ligament in order to improve joint recovery.

Conclusion: Preoperative planning for TKA must of course take into account bony deformation, but also preoperative joint motion. In the event of permanent flexion, the operative technique must be adapted. This allows correct position of the implant and improved joint motion.

Purpose: The purpose of this work was to report mid-term results of a series of 162 total knee prostheses with an all-polyethylene plateau.

Material and methods: Between 1989 and 1995, 162 posterior stabilised cemented HLS2 total knee prostheses with an all-polyethylene plateau were implanted during first intention arthroplasties performed by the same surgeon. 142 prostheses were reviewed at more than one year, three patients died, and 17 were lost to follow-up (10%). Clinical results were assessed with the IKS criteria. Complete x-ray data included pangonograms. Mean follow-up was 4.5 years.

Results: Ninety-six percent of the patients were satisfied or very satisfied and 95% had no pain or mild pain. Mean flexion was 114°. The mean postoperative knee score was 81/100 and mean function score was 64/100. Radiographic findings showed the good position of the implants with mean AFT at 178.6°, mean AFm at 89.1° and mean ATm at 89°. There were eight failures (4.9%) requiring replacement of a component, two for frontal laxity, three for patellar fracture, one for infection, one for aseptic loosening, and one for an oversized tibial plateau. Two revision procedures were performed without implant replacement, one for pain (biopsy) and one for arthrolysis.

Discussion: These 162 prostheses with an all-polyethyl-ene plateau were retained among a consecutive series of 893 HLS prostheses. We compared the present results with those of the metal-backed prostheses implanted in this series and with data in the literature. We found a significant correlation between the presence of tibial lucent lines and postoperative alignment defects, explained by the type of tibial component, in these 162 all-polyethyl-ene plateau prostheses. These lucent lines did not progress with time and had no clinical consequence.

Conclusion: Clinial and radiological results with total knee prostheses with an all-polyethylene plateau, i.e. without metal backing, were very good in this series. We analysed our experience in comparison with the literature, focusing on the advantages and disadvantages of these two types of components.

Purpose: The purpose of this work was to analyse functional results in patients with objective patellar instability who underwent surgery between 1988 and 1999.

Material and methods: One hundred eighty knees, 140 patients, were included in this series. Minimum follow-up was two years, and the mean follow-up was five years (range 24 – 152 months). The IKDC 99 subjective knee chart was used for postoperative assessment. This chart has ten items for sports activities and functional status of the knee for everyday activities. Eighty-three percent of the patients (118 patients) responded to the questionnaire.

Results: Clinical assessment was available for 98 patients (63%) and phone interview data for 29 (20%). Subjectively, 111 (94.87%) patients were very satisfied, five (4.27%) were satisfied, and one was dissatisfied. We assessed results by pain level (37.6% mild or weather-related pain), residual oedema, sensation of blockage (15.8%), instability, daily activities (68% with difficulty in the kneeling position), sports activity and level.

Discussion: Certain authors (Insall) question the pertinence of operating objective patellar instability because of the risk of secondary femoropatellar degeneration. For us, surgical treatment is indicated when there has been at least one dislocation associated with morphological anomalies. We have not observed any cases of femoroatellar degeneration among our patients who were operated on more than ten years ago. The patients’ own subjective assessment shows that surgical treatment with medialisation and/or lowering of the tibial tuberosity has been effective with a very excellent rate of satisfaction. The quality of the results is directly related to correct treatment of the lesions (for patients without recurrent dislocation) and systematic analysis of the different factors contributing to patellar instability (trochlear dyplasia, patellar height, quadriceps dyplasia, length of the patellar tendon). Our rate of revision appears to be low but was directly related to the young age of this population and is close to or above the revision rates observed in series with follow-ups greater than two years.

Conclusion: Surgery for objective patellar instability gives good mid- and long-term results. The subjective IKDC score allows precise self-evaluation. We have not been able to find any correlation between subjective results and objective results.