Introduction and Aims: Currently, multiple femoral component types and sizes exist for primary total hip arthroplasty. However, component sizes for small femoral geometry are generally not available. The purpose of this study is to present the short-term use of a femoral component with sizes that extend into small femoral morphometry applications.

Method: Between November 2001 and December 2003, 20 primary THA cases and three revision THA cases were performed utilising a non-cemented, dual threaded, cone shaped (DTCS) modular femoral component manufactured in off-the-shelf sizes, which include those sizes for small femora. The components are made of CoCr and include a size ‘Z’ (19mm proximal, 9mm distal) and a size ‘Y’ (17mm proximal, 8mm distal). Both components have hydroxyapatite coating for stimulating increased bone on-growth and a modular neck allowing intra-operative adjustments of leg length, version, offset and neck length.

Results: The average patient follow-up was 10 months (range 64 days to 27 months). There were 19 (83%) hips in which the ‘Z’ component was used, and four (17%) hips with the ‘Y’ component. Radiographic evaluation revealed well-fixed and positioned components with evidence of bone densing in areas in intimate contact with the DTCS component. Radiographic evidence of minor stress shielding was observed in the greater trochanter (Gruen Zone 1) and the proximal calcar/neck cut region (Gruen Zone 7). Two revision cases (8%) required the additional use of a 6cm modular extension component (MEC) to bridge a proximal femoral deficiency. Two cases (8%) required adjunctive strut allografting at the time of surgery to protect a thin or deficient femoral cortex. There were no reported postoperative complications related to the femoral component. There was no disassociation of the modular neck from the femoral stem and there was no incidence of femoral component fracture.

Conclusion: While expanding component profile offerings into larger sizes is common, developing similar component designs for abnormally small femora is uncommon, beyond the scope of the materials used and only done as a ‘custom’ order. The DTCS modular femoral component used affords a versatile option when presented with cases involving small femoral morphometry. We conclude that the DTCS component in smaller sizes is promising and warranted for continued use.

Introduction and Aims: The incidence and technical complexity of revision total hip arthroplasty (THA) has and will continue to increase dramatically. We report the results of revision THA using a non-cemented, dual threaded, cone shaped, (DTCS) modular femoral component.

Method: Between June of 1999 and July of 2003, 41 revision THAs using a DTCS modular femoral component. Fifty-four percent of the patients were male and 46% were female with an average weight of 84kg (std dev: 30kg, range 57–60 kg), an average height of 170cm (sdt dev: 9cm, range: 155–182 cm) and an average body mass index (BMI) of 26 (std dev: 4, range: 18–31). The average patient age was 71 years (std dev: 12 years, range: 39–85 years).

Results: The average patient follow-up was 16 months (range 6–49 months). The average Harris hip score (HHS) at the most recent time to follow-up was 76. Broken into the HHS component parts, the average pain score was 40 of a possible 44, average motion was nine of a possible nine, and average function was 28 of a possible 47. Radiographic evaluation revealed wellfixed and positioned components with evidence of bone densing in areas in intimate contact with the DTCS component. Radiographic evidence of minor stress shielding was observed in the greater trochanter (Gruen Zone 1) and the proximal calcar/neck cut region (Gruen Zone 7). Post-operative complications included recurrent infection in four (10%), subsequently resolved with IV antibiotics; dislocation in three (7%), successfully treated by closed reduction and protective bracing; aseptic loosening in one (2%), with femoral component revision to a larger size; intra-operative periprosthetic fracture in one (2%), treated with ORIF (bone, plate and screws); and a non-union of a pre-revision fracture with subsequent component loosening in one (2%). Regardless of the degree of femoral deficiency, there was no incidence of component disassociation or component fracture.

Conclusion: Revision THA is a demanding undertaking and involves multivariate technical challenges that may include mechanical and material considerations such as prosthetic loosening, prosthetic and periprosthetic fracture. We show that the use of a DTCS modular femoral component affords the surgeon results equal to those reported for revision THA and allows intra-operative versatility independent of bone quality.

Introduction and Aims: Minimal Invasive Surgery (MIS) in THR surgery offers potential advantages over standard techniques. A user-friendly surgical technique has been developed via the posterior approach to the hip using a single six to eight centimetre incision, and requiring no special instrumentation other than three long Homan retractors of standard design. The technique has been used to date in 80 sequential non-obese patients undergoing both uncemented and cemented THRs.

Method: Five cemented and 75 uncemented THR procedures were performed in the lateral position via a segment of the standard posterior approach incision, centred just behind the greater trochanter. The pre- and post-operative SF12, WOMAC, Harris hip score and Pain score were assessed prospectively; blood loss, theatre time and intra-operative and post-operative complications were charted, and compared with 40 matched standard incision patients. Cup and stem component positioning was assessed radiologically. The Body Mass Index (BMI) and the incision length were charted in each patient. The post-operative time to full weightbearing and stair climbing was charted.

Results: There was no statistical difference in SF12, WOMAC, Harris hip score and Pain score in the two groups of patients. Blood loss was slightly reduced, but theatre time and intra-operative and post-operative complications were not increased. Cup and stem positioning on x-ray was not compromised. Immediate full weightbearing was allowed, including stair climbing post-operatively in all patients.

Conclusion: MIS THR via the posterior approach is a safe and reproducible procedure, for both cemented and uncemented prostheses. It requires no special instrumentation or long learning phase for the experienced hip surgeon. Blood loss, theatre time and morbidity have not been increased, allowing a rapid discharge program as a routine.

Background: A totally new double-threaded cone-shaped modular femoral stem has been designed, using rotational rather than percussive hammer insertion of the prosthesis. The vertical height, the neck length, the neck anteversion angle and the medial offset can all be adjusted after preparation of the femoral canal has been completed.

Methods: The new stem design and the technique of insertion are described. A consecutive series of the first 110 hip joints in 103 patients were followed clinically and radiographically for an average of 28 months.

Results: The Harris hip score average rose from 43.6 points preoperatively to 91 points postoperatively. The pain score average changed from 7.9 points to 42 points, respectively. Thirteen hips (11.8%) had mid-thigh pain, most of them mild. One hip (0.9%) showed clinical and radiographic signs of early loosening and was revised.

Conclusions: The short-term clinical and radiographic outcomes were encouraging. The double-threaded cone-shaped stem locking mechanism was shown to be able to withstand the torsional and vertical forces applied to a hip-replacement prosthesis.

Introduction: The double threaded Cone Modular Hip Replacement System has been used in 114 patients as a primary prosthesis in over three years. No patient has been lost to follow up and all patients have been assessed postoperatively for the Harris Hip Score, Pain Score, Dexa analysis as well as plain X-rays.

Method: 114 patients requiring primary hip replacement were entered into a prospective clinical trial over a three year period. The Harris Hip Score, Pain Score and Dexa analysis (Luna 2000 program) and X-rays were assessed at six weeks, three months, six months, twelve months, two years and three years and results were compared with the preoperative figures. Length of hospital stay, discharge details (home or rehabilitation unit) and physiotherapy assessment of time to independent stair climbing was prospectively assessed.

Results: The Dexa analysis indicates a loss of bone at two years at Gruen’s zones one and seven of 25% and at zones two and six of approximately 20% with no increase or loss of bone in zones three, four and five.

The Harris Hip Scores and Pain Scores show a significant improvement comparing preoperative with postoperative results in this series.

One patient required revision of the femoral neck component for recurrent dislocation and three patients have significant rotational thigh pain due to varus implantation of the stem (the pilot has since been shortened and the diameter reduced by 1mm).

Conclusion: The double threaded cone shaped modular hip prosthesis stem allows immediate full weight bearing postoperatively. No prosthesis has loosened or subsided and the locking mechanism has been shown to gain immediate and long term fixation as a primary prosthesis stem.

Clinical assessment, X-rays and Dexa analysis indicate satisfactory results with good incorporation of the prosthesis by the bone.

Background: A total new double-threaded cone-shaped modular femoral stem has been designed, using rotational rather than percussive hammer insertion of the prosthesis. The vertical height, the neck length, the neck anteversion angle and the medial offset can all be adjusted after preparation of the femoral canal has been completed.

Methods: A consecutive series of the first 110 hip joints in 103 patients were followed clinically and radiographically for an average of 28 months.

Results: The mean Harris hip score rose from 43.6 points preoperatively to 91 points postoperatively. The mean pain score changed from 7.9 points to 42 points, respectively.

13 hips (11.8%) had mid-thigh pain, most of them mild. One hip (0.9%) showed clinical and radiographic signs of early loosening and was revised.

Conclusion: The short-term clinical and radiographic outcomes are encouraging. The double-threaded cone-shaped stem locking mechanism has been shown to be able to withstand the torsional and vertical forces applied to hip replacement prosthesis.

Background: Dual-energy X-ray absorptiometry has been validated as an accurate method for assessing periprosthetic bone loss around the femoral stem after uncemented total hip arthroplasty. A prospective longitudinal study was conducted to evaluate bone mineral density (BMD) changes around a series of double-threaded cone-shaped modular femoral stems.

Materials: 64 hips with implanted double-threaded cone-shaped femoral stem were scanned in the anteroposterior femoral plane using a Lunar DPXL densitometer with special software. The initial MBD scan was performed 2–4 weeks after the surgery and thereafter yearly for up to three years.

Results: Significant changes occurred during the first year after surgery. In the proximal femur the mean BMD decreased to 73%±17% (p< 0.001) in the calcar area and to 91%±13% (p< 0.001) in the greater trochanter region. In the middle part of the stem the mean BMD decreased to 86%±17% (p< 0.001) on the medial side and to 84%±12% (p< 0.001) on the lateral side. No significant changes occurred around the distal part of the stem. During the second and third postoperative years, small progressive changes in BMD were noticed in all Gruen zones, in keeping with age-related bone loss.

Conclusion: Significant decreases in BMD around the femoral stem prosthesis in the proximal parts of the femur were recorded during the first postoperative year. These changes may be explained by the metaphyseal-diaphyseal gripping prosthesis design. No significant distal changes were found.

Introduction: Dual-energy x-ray absorptiometry (DEXA) measurement is a valuable and accurate method of assessing periprosthetic bone loss around femoral stems.

Method: The cohort was 21 patients who underwent total hip arthroplasties with double-threaded, cone-shaped, modular, femoral stems and who already had a prosthetic contralateral hip. The contralateral hip arthroplasties were Autophur fully porous coated, Exeter cemented and Charnley cemented stems. DEXA measurements were performed in the anteroposterior femoral plane using a Lunar DPXL densitometer and analysed using the Lunar Orthopaedic Software Package, Version 1.7, designed for periprosthetic measurements. The initial measurement was performed between two and four weeks after the surgery as a baseline and then repeated after three, six, 12 and 24 months. The DEXA scan results were analysed comparing the bone density of the double-threaded cone-shaped modular femoral stem side with the contralateral side in a longitudinal study.

Results: The contralateral hip bone quality remained fairly constant in keeping with the maturity of the hip arthroplasties. The insertion of the double-threaded cone-shaped modular femoral stem caused the expected initial bone loss in Gruen zones one and seven due to proximal stress-shielding. Only minor bone loss occurred distally, reflecting good fixation and load transfer of the prosthesis.

Background: Dual-energy x-ray absorptiometry has been validated as an accurate method for assessing periprosthetic bone loss around the femoral stem after uncemented total hip arthroplasty. A prospective longitudinal study was conducted to evaluate bone mineral density (BMD) changes around a series of double-threaded cone-shaped modular femoral stems.

Methods: Sixty-two hips with implanted double-threaded cone-shaped femoral stems were scanned in the antero-posterior femoral plane using a Lunar DPXL densitometer with special software. The initial BMD scan was performed between two and four weeks after the surgery and thereafter yearly for up to three years.

Results: Significant changes occurred during the first year after surgery. In the proximal femur the mean BMD decreased to 73%, by17% in the calcar area and to 91%, by13% in the greater trochanter region. In the middle part of the stem the mean BMD decreased to 86%, by 17% on the medial side and to 84%, 12% on the lateral side. No significant changes occurred around the distal part of the stem. During the second and third postoperative years, small progressive changes in BMD were noticed in all Gruen zones, in keeping with age-related bone loss.

Conclusions: Significant decreases in BMD around the prosthetic femoral stem in the proximal parts of the femur were recorded during the first postoperative year. These changes may be explained by the metaphyseal-diaphyseal gripping prosthesis design. No significant distal changes were found.

A femoral stem using a double threaded cone locking mechanism has been developed down under. Over 400 prostheses have been implanted as primary, revision and replacement prostheses over the last 4 years. Stem insertion is achieved by a gentle screw home mechanism and does not use the “hammer and nail” insertion principle.

Design

The prosthesis has two components:

A cone shaped stem

The stem body externally is a slowly tapering hydroxyapatite coated cone, with a distal pilot and two differing speed external threads. The parallel threads strongly resist derotation of the prosthesis in the bone and impart rotatory stability. The cone shape imparts excellent vertical stability.

Full four-vector adjustability is available at the end of stem preparation:

Vertical height (leg length)

Design Advantages

The locking mechanism gains immediate and longterm vertical and torsional stability in the femur.

Immediate full weight bearing is possible, especially in primary total hip replacements.

The locking mechanism grips equally well in the metaphysis and proximal or distal diaphysis of the femur.

Bulk structural allograft may not be necessary even in the severely deficient proximal femur.

The prosthesis can be used in wide medullary canals.

The early clinical experience with this prosthesis will be presented.

Osteotomy is an alternative treatment for unicompartmental disease (UCJD) of the knee with or without patellofemoral disease. Untreated, UCJD does progress. The ideal patient is young, with progressive early disease, high activity and a high pain threshold. Preoperative planning is essential and should include arthroscopy.

In genu varum, the aim is to transfer the weight-bearing axis from the medial to the lateral compartment. This is best achieved by a high valgus closing wedge, which corrects close to the deformity and has a high union rate. At 5–7 years, good or excellent results vary from 75–85%. Better results are achieved with a low adduction moment, metaphyseal bowing, early disease, low body weight in younger patients; over correction to 5° is important.

Complications and poor outcomes have been reported, but recent long-term follow-ups show that an incomplete osteotomy with precise jigging, compression fixation, early mobilisation, and weight-bearing eliminates many of these problems. Recent studies have shown that the outcome of post-osteotomy TKA is no worse than primary TKA that patella baja is related to postoperative immobilisation and that uni’s are more difficult to revise because of bone loss.

Supracondylar osteotomy is preferred to HTO for genu valgum. Correction should be to beyond 6° of mechanical varus. A lateral opening wedge using a toothed plate is preferred, as it allows easy access to the lateral compartment through the same incision and is more precise.

Osteotomy, far from being obsolete, has an increasing role in joint resurfacing procedures, is less of a gamble, and certainly deserves a “seat at the table”. It may be combined with other reconstructive procedures.