Richard J. Beaver

Good Alignment After Total Knee Arthroplasty Leads to Faster Rehabilitation and Better Function

The aim of this study was to identify what aspects of implant alignment and rotation affect functional outcome after total knee arthroplasty (TKA). One hundred and fifty-nine total knee arthroplasties were performed at the authors institution between May 2003 and July 2004. All patients underwent an objective and independent clinical and radiological assessment before and after surgery. A computed tomography scan was performed at 6 months. The alignment parameters that were measured included sagittal femoral, coronal femoral, rotational femoral, sagittal tibial, coronal tibial, and femorotibial mismatch. The cumulative error score, which represents the sum of the individual errors, was calculated. Functional outcome was measured using the Knee Society Score. Good coronal femoral alignment was associated with better function at 1 year (P = .013). Trends were identified for better function with good sagittal and rotational femoral alignment and good sagittal and coronal tibial alignment. Patients with a low cumulative error score had a better functional outcome (P = .015). These patients rehabilitated more quickly and their length of stay in hospital was 2 days shorter.

Corrosion at the neck-stem junction as a cause of metal ion release and pseudotumour formation

We present a series of 35 patients (19 men and 16 women) with a mean age of 64 years (36.7 to 75.9), who underwent total hip replacement using the ESKA dual-modular short stem with metal on-polyethylene bearing surfaces. This implant has a modular neck section in addition to the modular head. Of these patients, three presented with increasing post-operative pain due to pseudotumour formation that resulted from corrosion at the modular neck-stem junction. These patients underwent further surgery and aseptic lymphocytic vaculitis associated lesions were demonstrated on histological analysis. Retrieval analysis of two modular necks showed corrosion at the neck-stem taper. Blood cobalt and chromium levels were measured at a mean of nine months (3 to 28) following surgery. These were compared with the levels in seven control patients (three men and fourxa0women) with a mean age of 53.4 years (32.1 to 64.1), who had an identical prosthesis and articulation but with a prosthesis that had no modularity at neck-stem junction. The mean blood levels of cobalt in the study group were raised at 50.75 nmol/l (5 to 145) compared with 5.6 nmol/l (2 to 13) in control patients. Corrosion at neck-stem tapers has been identified as an important source of metal ion release and pseudotumour formation requiring revision surgery. Finite element modelling of the dual modular stem demonstrated high stresses at the modular stem-neck junction. Dual modular cobalt-chrome hip prostheses should be used with caution due to these concerns.

Penetration and shear strength of cement-bone interfaces in vivo

Using sham replacement of the proximal femur in adult mongrel dogs, shear strength at the interface between polymethylmethacrylate bone cement and cancellous bone has been found to be linearly dependent on the depth of penetration of the cement into the bone. Shear strength at the interface was increased by 82% and penetration by 74% when distal bone plugging, pressure lavage, and pressurized insertion of cement were employed. Use of a lower-viscosity cement gave a further 18% increase in penetration and shear strength. There was no film of blood at the cement-bone interface with pressurized insertion of Simplex P and Palacos R cements.

Computer Navigation vs Conventional Total Knee Arthroplasty: Five-Year Functional Results of a Prospective Randomized Trial

Seventy-one patients were randomly allocated to undergo either computer-navigated or conventional arthroplasty. A statistically significant improvement in alignment was seen in the computer-navigated cohort. Five-year functional outcome was assessed using the Knee Society, Short Form-36, Western Ontario and McMaster Universities Osteoarthritis Index, and a patient satisfaction score. At 5 years, 46 patients were available for assessment (24 navigated and 22 conventional knees). No patients had undergone revision. No statistically significant difference was seen in any component of any measure of outcome between navigated and conventional cohorts. Longitudinal data showed function to be well maintained with no difference in functional score between 2 and 5 years in either cohort. Despite achieving better alignment, 5 years postoperatively, the functional outcome with computer-navigated knee arthroplasty appears to be no different to that implanted using a conventional jig-based technique.

Computer navigation of the acetabular component: A CADAVER RELIABILITY STUDY

Our aim was to assess the intra- and inter-observer reliability in the establishment of the anterior pelvic plane used in imageless computer-assisted navigation. From this we determined the subsequent effects on version and inclination of the acetabular component. A cadaver model was developed with a specifically-designed rod which held the component tracker at a fixed orientation to the pelvis, leaving the anterior pelvic plane as the only variable. Eight surgeons determined the anterior pelvic plane by palpating and registering the bony landmarks as reference points. The exact anterior pelvic plane was then established by using anatomically-placed bone screws as reference points. The difference between the surgeons was found to be highly significant (p < 0.001). The variation was significantly larger for anteversion (sd 9.6 degrees ) than for inclination (sd 6.3 degrees ). The present method for registering pelvic landmarks shows significant inaccuracy, which highlights the need for improved methods of registration before this technique is considered to be safe.

Three-Dimensional Component Alignment and Functional Outcome in Computer-Navigated Total Knee Arthroplasty : A Prospective, Randomized Study Comparing Two Navigation Systems

Computer navigation in total knee arthroplasty produces better component alignment than conventional techniques. Different navigation systems exist. We undertook a prospective, randomized study comparing 2 navigations systems (Stryker Full Navigation and Stryker Articular Surface Mounted [ASM] navigation systems). Three-dimensional component alignment (Perth computed tomographic knee protocol) and function at 1 year (Knee Society Scores) were assessed. Forty patients participated (20 fully navigated and 20 ASM-navigated total knee arthroplasties). Cohorts were well matched according to sex, age, and body mass index. No statistically significant difference was seen in any parameter of 3-dimensional component alignment or function between cohorts. Operative time for the ASM cohort was significantly less than the fully navigated cohort (P = .001). Both systems performed equally well, and therefore, surgeon preference should determine which system is used.

Abnormal Quantitative Sensory Testing is Associated With Persistent Pain One Year After TKA

BackgroundUp to 15% of patients report at least moderate persistent pain after TKA. Such pain may be associated with the presence of widespread hyperalgesia and neuropathic-type pain.Questions/purposesWe asked if there was a difference among patients who report moderate to severe pain or no pain at least 12xa0months after TKA regarding (1) pressure pain threshold, (2) thermal (cold/heat) pain and detection thresholds, and (3) self-reported neuropathic pain.Patients and MethodFifty-three volunteers were recruited from patients reporting no pain or moderate to severe pain, according to the Knee Society Score©. Differences between the moderate-to-severe and no-pain groups regarding pressure pain, heat and cold thresholds, and self-reported neuropathic-type pain were analyzed using independent t-tests.ResultsPatients in the moderate-to-severe pain group exhibited reduced pressure pain threshold in the knee with the TKA (pxa0=xa00.025) and at the elbow (pxa0=xa00.002). This group also showed greater pain sensitivity to cold at the knee (pxa0=xa00.008) and elbow (pxa0=xa00.010), and increased heat pain sensitivity at the elbow (pxa0=xa00.032). Cold and heat detection thresholds were impaired in this group at the elbow (cold, pxa0=xa00.034; heat, pxa0=xa00.010), although only heat detection was impaired at the knee (pxa0=xa00.009). The moderate-to-severe pain group also reported more neuropathic-type pain (pxa0=xa00.001).ConclusionPersistent pain after TKA was associated with widespread pressure, cold hyperalgesia, and greater neuropathic-type pain.Level of EvidenceLevel III, prognostic study.

Stiffness After Total Knee Arthroplasty: Does Component Alignment Differ in Knees Requiring Manipulation?: A Retrospective Cohort Study of 281 Patients

This study aims to evaluate component alignment in a large cohort of total knee arthroplasties (TKAs) and ascertain whether alignment in TKAs undergoing postoperative manipulation under anesthetic is significantly different from those achieving good function. A retrospective review of 281 consecutive primary TKAs was performed. All TKAs underwent computed tomographic scanning (Perth computed tomography knee protocol). Of 281 TKAs, 21 (7.4%) underwent manipulation, performed at a mean of 8.1 weeks (range, 3-14 weeks) after surgery. No statistically significant difference was seen between groups for any of 12 parameters of alignment. Postoperative stiffness with the need for manipulation under anesthetic is multifactorial in origin. This study found insufficient evidence to support the theory that component alignment contributes significantly to the etiology of this difficult problem.

Morbidity of navigated vs conventional total knee arthroplasty: a retrospective review of 327 cases.

A retrospective review of 146 patients undergoing navigated total knee arthroplasty (NTKA) and 181 patients undergoing conventional total knee arthroplasty (CTKA) was undertaken to establish whether NTKA, with its avoidance of intramedullary instrumentation, resulted in less early postoperative morbidity than CTKA. Cohorts were well matched in terms of age, sex, body mass index, and American Society of Anesthesiologists grade. Statistically significantly longer operative and tourniquet times were seen with NTKA. Blood transfusion requirements were significantly higher in CTKA. No statistically significant differences were seen in any other measure of postoperative morbidity (length of stay, hemoglobin drop, transfusion rate, postoperative anemia, time to achieve 70° flexion, and thromboembolic phenomena). In large, well-matched cohorts, NTKA offered no benefit in terms of early postoperative morbidity when compared with conventional jig-based techniques.

Computer navigation of the acetabular component

Our aim was to assess the intra- and inter-observer reliability in the establishment of the anterior pelvic plane used in imageless computer-assisted navigation. From this we determined the subsequent effects on version and inclination of the acetabular component. A cadaver model was developed with a specifically-designed rod which held the component tracker at a fixed orientation to the pelvis, leaving the anterior pelvic plane as the only variable. Eight surgeons determined the anterior pelvic plane by palpating and registering the bony landmarks as reference points. The exact anterior pelvic plane was then established by using anatomically-placed bone screws as reference points. The difference between the surgeons was found to be highly significant (p < 0.001). The variation was significantly larger for anteversion (sd 9.6 degrees ) than for inclination (sd 6.3 degrees ). The present method for registering pelvic landmarks shows significant inaccuracy, which highlights the need for improved methods of registration before this technique is considered to be safe.