Paul R. Kim

Major complications associated with femoral nerve catheters for knee arthroplasty: a word of caution.

One thousand one hundred ninety patients underwent knee arthroplasty between January 2004 and July 1, 2007, and received an indwelling continuous infusion femoral catheter for postoperative ropivicaine pump infusion. Catheters were placed using electrical stimulation guidance. For the initial 469 patients (group 1), the continuous infusion ran for 2 to 3 days. In 721 patients, the infusion was discontinued 12 hours after surgery. There were 9 femoral nerve palsies (2 in group 1, 7 in group 2) and 8 major falls (0.7%). The overall complication rate was 1.5%, and the risk of permanent nerve injury was 0.2%. Patients should be made aware of these complications as part of the usual informed consent process before using this technique for postoperative pain control after knee arthroplasty. We did not observe fewer falls when the continuous infusion was stopped 12 hours after surgery.

Initial experience with the oxford unicompartmental knee arthroplasty.

Our initial experience with mobile bearing medial compartment unicompartmental arthroplasty (UKA) is presented to highlight lessons that have been learned to avoid short-term failures. Consecutive cases of the Oxford medial UKA performed between February 2001 and April 2006 were reviewed to derive those cases that were revised to total knee arthroplasty (TKA). There were 545 patients available with mean age and body mass index of 65.0 and 30.1, respectively. At final follow-up, 32 patients were revised for lateral compartment arthritis, aseptic component loosening, persisting medial or anterior pain and dislocated meniscal bearing. Revisions were performed with primary unconstrained TKA implants with no stems or wedges required. Our results seem to reflect those seen in registries confirming an earlier higher revision rate and highlight the technical issues of overstuffing the compartment, inadequate cementation technique, and strict adherence to patient selection.

Unicompartmental Knee Arthroplasties Revised to Total Knee Arthroplasties Compared With Primary Total Knee Arthroplasties

We studied the technical operative features and the subjective outcomes of 63 patients requiring a revision to a total knee arthroplasty (TKA) for failed Oxford medial unicompartmental knee arthroplasty. We compared this revision study group to a contemporary control cohort of 126 patients who underwent primary TKAs. The 2 groups from the same institution had a minimum follow-up of 2 years and were retrospectively matched 1:2 for age, sex, body mass index, and follow-up time. Length of stay and hemoglobin level drop were similar. Technically, the revision group required larger polyethylene inserts (P < .001) and longer tourniquet times (P < .001) with 15 of these patients needing augments, grafts, and/or stems. Subjectively, the revision groups mean total Western Ontario and McMaster Universities Arthritis Index score was 25.8 ± 20.2, thus less satisfactory compared with the control group (19.8 ± 15.3) at a mean follow-up of 3.1 years (P = .03). A revision unicompartmental knee arthroplasty to TKA is technically more difficult and functionally less satisfactory at last follow-up when compared with a primary TKA.

Repeated Early Failure of a Newly Designed Hinged Knee System

We report a case of acute and recurrent accelerated wear of the polyethylene bushings of the hinge mechanism in the Zimmer Segmental Knee System. This resulted in an unacceptable recurvatum deformity leading to multiple revision knee operations, which was unexpected in a modern design hinged knee system. A custom modification of the original design was used to prevent further recurvatum deformity. The current design of the hinge post mechanism in this system appears to be inadequate, which led to the development of a significant recurvatum deformity in our patient. Surgeons should be aware of this potential complication when considering the use of this revision knee system.

Treatment of Retroacetabular Osteolysis with Calcium Sulfate and Retention of Original Components

Restoration of retroacetabular bone stock by curettage and grafting with synthetics would obviate the need for autograft or allograft bone and prevent bone loss associated with revision. We conducted a clinical and radiographic review of 7 patients with progressive retroacetabular osteolysis. The size of the lesions ranged from 3.1 x 2.0 to 9.0 x 5.3 cm(2). All patients were treated with curettage and filling of the defects with calcium sulfate. Mean follow-up time was 48 months. On follow-up evaluation, there was resolution of 4 lesions, good osseous integration of 2 lesions, and no progression of 1 lesion. Curettage and grafting of progressive retroacetabular osteolysis with calcium sulfate and retention of components result in good osseous integration of the graft and halt the progression of lysis.

A randomised controlled trial of cemented and cementless femoral components for metal-on-metal hip resurfacing: a bone mineral density study

The primary purpose of this study of metal-on-metal (MoM) hip resurfacing was to compare the effect of using a cementless or cemented femoral component on the subsequent bone mineral density (BMD) of the femoral neck. This was a single-centre, prospective, double-blinded control trial which randomised 120 patients (105 men and 15 women) with a mean age of 49.4 years (21 to 68) to receive either a cemented or cementless femoral component. Follow-up was to two years. Outcome measures included total and six-point region-of-interest BMD of the femoral neck, radiological measurements of acetabular inclination, neck-shaft and stem-shaft angles, and functional outcome scores including the Harris hip score, the Western Ontario and McMaster Universities Osteoarthritis Index and the University of California at Los Angeles activity scale. In total, 17 patients were lost to follow-up leaving 103 patients at two years. There were no revisions in the cementless group and three revisions (5%) in the cemented group (two because of hip pain and one for pseudotumour). The total BMD was significantly higher in the cementless group at six months (p < 0.001) and one year (p = 0.01) than in the cemented group, although there was a loss of statistical significance in the difference at two years (p = 0.155). All patient outcomes improved significantly: there were no significant differences between the two groups. The results show better preservation of femoral neck BMD with a cementless femoral component after two years of follow-up. Further investigation is needed to establish whether this translates into improved survivorship.

Histologic analysis of fetal ulnar variance

Twenty-eight fetal wrists aged 5 to 21 weeks gestation were examined histologically to assess ulnar variance. There was a trend from ulna negative to ulna neutral among this population. Of 10 wrists in group I (5-8 weeks gestation), 8 were ulna negative and 2 were ulna neutral. Of nine wrists in group II (11-13 weeks gestation), three were ulna negative and six were ulna neutral. Of nine wrists in group III (18-21 weeks gestation), two were ulna negative and seven were ulna neutral. Overall, 13 embryos demonstrated an ulna negative variance; the remainder had ulna neutral variance. These results are significantly different than the incidence of ulnar variance in adults. With growth, factors must occur that change this fetal relationship of radius to ulna.

A Single-Center Experience With a Titanium Modular Neck Total Hip Arthroplasty

BACKGROUND Added modular junction has been associated with implant-related failures. We report our experience with a titanium-titanium modular neck-stem interface to assess complications, possible clinical factors influencing use of neck modularity, and whether modularity reduced the incidence of dislocation. METHODS A total of 809 total hip arthroplasties completed between 2005 and 2012 from a prospectively collected database were reviewed. The mean follow-up interval was 5.7 years (3.3-10.3 years). Forty-five percent were male (360 of 809), and 55% were female (449 of 809). All stems were uncemented PROFEMUR TL (titanium, flat-tapered, wedge) or PROFEMUR Z (titanium, rectangular, dual-tapered) with a titanium neck. RESULTS Increased modularity (anteverted/retroverted and anteverted/retroverted varus/valgus (anteverted/retroverted + anteverted/retroverted varus/valgus) was used in 39.4% (135 of 343) of cases using the posterior approach compared with 6.8% (20 of 293) of anterior and 23.7% (41 of 173) of lateral approaches. Four males sustained neck fractures at a mean of 95.5 months (69.3-115.6 months) after primary surgery. Overall dislocation rate was 1.1% (9 of 809). The posterior approach had both the highest utilization of increased modularity and the highest dislocation rate (2.3%), of which the most were recurrent. The anterior (0.3%) and lateral (0%) approaches had lower dislocation rates with no recurrences. CONCLUSION At a mean 5.7 years, our experience demonstrates a low neck fracture (0.5%) and a low dislocation rate (1.1%). Use of increased modularity may not improve dislocation risk for the posterior approach. Continued surveillance of this group will be necessary to determine long term survivorship of this modular titanium implant.

Primary total knee arthroplasty twenty years after distal femoral cement augmentation of a giant cell tumor.

We present a case of knee reconstruction 20 years after treatment of a giant cell tumor (GCT) with curettage and cementation. There is currently an ongoing debate whether cement or allograft bone is the preferred material for filling the void after GCT curettage. In this case we were able to readily implant a primary total knee replacement without disturbing the existing well-interdigitated large cement bolus and did not require any stems or augments for the reconstruction. Given the ease of TKR implantation in this patient, we feel that the use of cement following curettage of a GCT lesion is a better choice than allograft bone which may not provide enough structural support for the knee reconstruction and lead to a much more extensive procedure.

Metal on Metal Hip Resurfacing in Patients 45 Years of Age and Younger at Minimum 5-Year Follow-Up

BACKGROUND Metal on metal hip resurfacing (MoM-HR) is an alternative to total hip arthroplasty in young and active patients. The purpose was to determine the survivorship of MoM-HR procedures performed in patients aged 45 years and younger assessing patient-reported outcome measures (PROMs) at minimum 5-year follow-up. METHODS All 217 patients equal to or younger than 45 years of age at the time of surgical intervention presenting to our center with MoM-HR between May 2002 and May 2011 were prospectively followed. Baseline demographic data, preoperative and postoperative radiographic measurements, and validated PROMs were obtained (Hip Disability and Osteoarthritis Outcome Score, Western Ontario and McMaster Universities Osteoarthritis Index, and University of California, Los Angeles Activity Score). Survivorship was calculated using Kaplan-Meier analysis, and risk factors for failure were identified using multivariate regression analysis. RESULTS The overall survivorship excluding septic failures was 94.6% and 93.8% at 5 and 10 years, respectively. Aseptic loosening of the acetabular component was the most common mode of failure (11/20 cases). Gender, head size, and acetabular abduction angle had no significant effect on survivorship. Significant improvements in PROMs were seen for Hip Disability and Osteoarthritis Outcome Score, Western Ontario and McMaster Universities Osteoarthritis Index, and University of California, Los Angeles Activity Scale (P < .001). CONCLUSION This study indicates that MoM-HR is a suitable option for young individuals, as demonstrated through improved functional scores and low revision rates. The survivorship of HR in the younger than 45 age-group was similar to that of total hip arthroplasty, as well as HR in older patients. Given the proposed benefits of HR, this procedure may be viewed as a viable option in patients aged younger than 45 years.