The benefit of using acetabular screws in primary total hip arthroplasty (THA) has been questioned in recent years. The disadvantages of using screws include increased operative time, risk of injury to surrounding neurovascular structures and metal ware breakage. Recent large registry studies have reported that screws do not confer a protective effect against acetabular loosening or the presence of osteolysis. Other studies have even described an increased risk of aseptic acetabular loosening with the selective use of screws. We report findings from a multicentre cohort study.

This large cohort study compared clinical outcomes between primary acetabular components that were inserted with and without screws. Independent variables included the presence (or absence) of screws, the total number of screws used and the cumulative screw length (CSL). Outcome measures included all-cause revision, acetabular component revision and acetabular component loosening. Statistical software (Stata/IC 13.1 for Mac [64-bit Intel]) was used to conduct all statistical analyses. A p-value < 0 .05 taken to be significant.

There were 4,583 THAs performed in total. Screws were used in 15.9% (n=733). At a mean follow-up of 5.2 years, the all-cause revision rate in the screw cohort was 1.5% compared to 0.83% in the no screw cohort (p=0.085). There was no difference in acetabular component revision rates for screws (3/733, 0.41%) versus no screws (12/3,850, 0.31%) (p=0.439). The rate of acetabular loosening noted during the time of revision surgery was significantly higher when screws were used in the index procedure (2/733, 0.2%) compared to the no screw cohort (1/3,850, 0.02%) (p=0.017). There was no difference in outcomes when stratifying by the number of screws used or the cumulative screw length.

Primary acetabular components do not require screws for fixation. All cause revision rates and acetabular component revision rates are comparable for the screw and the no screw cohorts. The rate of acetabular component loosening, as observed during revision surgery, is significantly higher when screws are used in the index total hip replacement.

Background

The current orthopaedic literature demonstrates a clear relationship between acetabular component positioning, polyethylene wear and risk of dislocation following Total Hip Arthroplasty (THA). Problems with edge loading, stripe wear and squeaking are also associated with higher acetabular inclination angles, particularly in hard-on-hard bearing implants.

The important parameters of acetabular component positioning are depth, height, version and inclination. Acetabular component depth, height and version can be controlled with intra-operative reference to the transverse acetabular ligament.

Control of acetabular component inclination, particularly in the lateral decubitus position, is more difficult and remains a challenge for the Orthopaedic Surgeon. Lewinnek et al described a ‘safe zone’ of acetabular component orientation: Radiological acetabular inclination of 40 ± 10° and radiological anteversion of 15 ± 10°.

Accurate implantation of the acetabular component within the ‘safe zone’ of radiological inclination is dependent on operative inclination, operative version and pelvic position.

Traditionally during surgery, the acetabular component has been inserted with an operative inclination of 45°. This assumes that patient positioning is correct and does not take into account the impact of operative anteversion or patient malpositioning.

However, precise patient positioning in order to orientate acetabular components using this method cannot always be relied upon. Hill et al demonstrated a mean 6.9° difference between photographically simulated radiological inclination and the post-operative radiological inclination. The most likely explanation was felt to be adduction of the uppermost hemipelvis in the lateral decubitus position. The study changed the practice of the senior author, with target operative inclination now 35° rather than 40° as before, aiming to achieve a post-operative radiological inclination of 42° ± 5°.

Ideal cup positioning remains elusive both in terms of defining and achieving target.

Our aim is to restore original anatomy by using the Transverse Acetabular Ligament (TAL). In the normal hip TAL and labrum come beyond the equator of the femoral head therefore if the definitive cup is positioned such that: It is cradled by the TAL; Is ideally no more than 4mm greater in diameter than the original femoral head; Sits just deep to the plane of TAL and labrum (this means that normally we leave the fat pad intact and do not ream down to the true floor).

That should restore joint center in terms of height and offset. If the face of the cup is then positioned parallel and just deep to the TAL and psoas groove that should restore original version. We still use TAL for version in dysplasia because we believe the TAL and labrum compensate for any underlying bony abnormality. However in dysplasia the TAL and labrum fall short of original femoral head equator and therefore in such cases we ream down to the true floor if necessary and use a cup which is often smaller than the original head.

Inclination represents a greater challenge and TAL should not be used as an aid to inclination. Our research has shown that errors in postoperative x-ray inclination above 50 degrees are generally caused by errors in patient positioning when in lateral decubitus. Consequently great care needs to be taken when positioning the patient.

Historically correction of deformity in primary TKA has involved release of collateral ligaments to correct deformity. This has been common to both measured resection and gap balancing techniques but particularly the former. Essentially the collateral ligaments have been released to balance the bone cuts. Another philosophy is to consider that the collateral ligaments do not contract and should never be released. After sacrificing both cruciates I use a tibia first technique. The AP femoral cuts are done by using collateral ligament tension to set femoral rotation and create a rectangular flexion gap which is then measured

A five degree conservative or precut is then made on the distal femur. Critically all osteophytes have now been removed. The extension gap is assessed using a spacer block. In a varus knee the definitive cut is frequently made in more varus to create a balanced extension gap to equal the flexion gap. It is rare to have to release the posteromedial capsule.

In contrast in severe fixed valgus the posterolateral capsule frequently has be cut before the definitive distal femora cut is made. The latter is often in more valgus. I never resurface the patella but ensure good patellar tracking after inserting a cementless mobile bearing knee which is used irrespective of deformity. I am more concerned about gap balance than the mechanical axis.

Essentially the concept proposed is to cut the bone to balance the soft tissues as opposed to the reverse. The aim is to restore pre-morbid alignment and not necessarily a neutral mechanical axis.

Salvage Total Hip Arthroplasty (THA) presents a viable solution following failed treatment of a hip fracture. Several studies have suggested higher complication rate including high dislocation rate associated with salvage THA. The present study evaluates the results and complications of hip arthroplasty performed as a salvage procedure after the failed treatment of a hip fracture and comparison made to Primary THA in osteoarthritis (OA). Between 1992 and 2007, 53 patients with a mean age of seventy years were treated with THA after the failed treatment of a hip fracture under the care of a single surgeon. The indication for conversion arthroplasty was Avascular necrosis head – 24(45.3%), screw cut out – 6 (11.3%), non-union – 2(3.8%), Displaced fracture – 2(3.8%), Secondary OA – 19 (35.8%). The implants retrieved were Cannulated screws – 3, Sliding plate and screw – 46, Spline plate – 2, Smith Petersons nail – 1, Martin Plate – 1. This group of patients were matched for age, sex, side, and ASA grading with a group of 59 patients who underwent THA for primary osteoarthritis (THA-OA group). Posterior approach was used in all cases. Four patients (7.5%) required grafting of cup and 21 patients (39.6%) required soft tissue release. The average blood loss was 555 ml, mean duration of surgery was 85.5 min, average inpatient stay was 6.7 days. Cemented THA was used in 43 patients and Cementless THA in 10 patients. At one year follow up there were no dislocations, one patient had an undisplaced femoral fracture treated in Spica. Three patients had broken screws; one patient with shortening > 1 inch. There was one revision for deep infection. The mean Harris Hip Score (HHS) improved from 28.4 to 82.5 at one year, while the Oxford Hip score (OHS) improved from 50.9 to 21.9 (Old system). When the scores were compared to the THA-OA group there was no difference in the oxford hip scores and the the mean one year HHS in the THA-OA group was slightly higher than the group with salvage THA, but the difference was not statistically significant. Hip arthroplasty is an effective salvage procedure in patients with prior surgery for hip fracture. Most patients have good pain relief and functional improvement. Despite the operative challenges, remarkably few serious orthopaedic complications were associated with this procedure in the present study.

Increasing knee flexion following total knee arthroplasty (TKA) has become an important outcome measure. Surgical technique is one factor that can influence knee motion. In this study, it was hypothesised that stripping of the posterior knee capsule could improve flexion and range of motion (ROM) following TKA. Patients who were undergoing TKA were prospectively randomised into two groups - one group (62 patients) were allocated stripping of the posterior knee capsule (PCS), the other group (66 patients) no stripping (no-PCS). The primary outcome was change in flexion and ROM compared to pre-operative measurements at three time points; after wound closure, 3months and 1year post-operatively. Secondary outcomes were absolute measurements of flexion, extension, ROM and complications. All operations were performed by a single surgeon using the same implant and technique. All patients received identical post-operative rehabilitation. There was a significant gain in flexion after wound closure in the PCS group (p=0.022), however there was no significant difference at 3months or 1year post-operatively. Absolute values of extension (p=0.008) and flexion (p=0.001) 3months post-operatively were significantly reduced for the PCS group. The absolute value of ROM was significantly higher for the no-PCS group at 3months (p=0.0002) and 1year (p=0.005). There were no significant difference in the rate of complications. Posterior capsular stripping causes a transient increase in flexion that does not persist post-operatively. We do not recommend routine stripping of the posterior knee capsule in patients undergoing TKA.