This article quantifies pain differences in the immediate postoperative period between patients undergoing total hip arthroplasty (THA) and metal-on-metal hip resurfacing (MoMHR). Patients less than 65 years old indicated for either a primary MoMHR or THA were screened for consent. A total of 51 patients completed the study. Controlling for confounding factors, patients having MoMHR experienced significantly less pain at 24 hours than patients having THA. The MoMHR cohort experienced a significantly shorter length of stay than the THA cohort. MoMHR shows a significantly lower pain level at 24 hours than THA and a significantly earlier discharge.
Both total hip resurfacing and total hip arthroplasty are viable surgical options for properly indicated patients less than the age of 65 years, although longer-term survivorship is waited for the former.
Controversy remains about whether there is a clear front-runner in the treatment of end-stage hip disease in the young male osteoarthritic patient.
Theoretic advantages to resurfacing include the removal of less bone stock, which may provide a better femoral bone foundation for future revision to total hip arthroplasty if needed.
By removing less bone, there is a theoretic advantage in the immediate postoperative period because of less pain.
This article prospectively and quantitatively compares immediate postoperative pain between patients less than the age of 65 years undergoing total hip resurfacing or total hip arthroplasty.
With the excellent clinical outcomes and longevity seen with total hip arthroplasty (THA), its use has expanded into an increasingly young, more active patient population. Concurrent resurgence of third-generation metal-on-metal hip resurfacing (MoMHR) technology, with encouraging short-term to midterm clinical results have offered another viable option for an expanding, young patient population. Lack of long-term follow-up and comparable midterm results continue to fuel the debate between THA and MoMHR.
Among the proposed benefits of MoMHR are the qualities that theoretically indicate use for a young patient population. Some reports indicate lower wear rates with metal-on-metal articulation thus offering possible longer survival. Large-diameter component articulation also decreases dislocation risk. Less bone stock resection compared with a standard THA offers bone conservation, which theoretically may facilitate any future revision surgery. There is also the potential for less pain in the perioperative period with such bone conservation, even in the face of the larger incision typically required of MoMHR.
Thus, questions for this prospective study comparing MoMHR with THA in patients younger than 65 years old are: do patients having MoMHR experience less postoperative pain than patients having THA? If so, are the greatest differences observed at 3, 6, 24, or 48 hours following surgery? If so, does significantly lower postoperative pain equate to significantly higher patient satisfaction and/or a lower length of stay (LOS)?
Patients and methods
This study was reviewed and approved by the ethical committee of our institutional review board. All patients were screened and, if inclusion criteria were met, informed consent was obtained with the option of withdrawing from the study at any time. Inclusion criteria were patients less than 65 years old scheduled to undergo either a primary MoMHR or THA performed by 2 of the senior authors (JAG or WBM). Exclusion criteria included those who had previously undergone any type of surgery affecting the ipsilateral or contralateral hips and/or knees, including arthroscopy; those scheduled for a bilateral procedure; those unable to receive spinal anesthesia and/or receive our standard postoperative pain management protocol; and those patients with excessive chronic pain that would require postoperative patient-controlled analgesia (PCA) or consultation with pain management specialists.
From June 2008 to September 2009, 193 patients were screened for this study. A total of 54 patients were consented, but 3 subsequently were withdrawn (2 unable to receive spinal anesthesia; 1 withdrew, did not want further questioning), yielding 51 total patients who enrolled and completed the study, with a total of 29 in the MoMHR cohort and 22 in the THA cohort ( Fig. 1 ). Of the remaining 140 excluded patients, 53 had prior surgery, 49 were older than 65 years of age, 20 refused consent, 8 patients did not have adequate third party data personnel available to obtain data, 5 patients required specialized postoperative pain management along with PCA, 3 patients were indicated for bilateral procedures, and 2 patients canceled their scheduled surgeries (see Fig. 1 ).
Mean age did not differ significantly between the MoMHR and THA groups (48.5 ± 8.7 years vs 52.1 ± 12.6 years, P = .22, Table 1 ). In the MoMHR group, all patients had a preoperative diagnosis of osteoarthritis (OA), whereas the THA cohort had 18 with OA, 3 with avascular necrosis (AVN), and 1 with hip dysplasia; these differences were not significant ( P = .057, Table 1 ). Mean body mass index (BMI, calculated as weight in kilograms divided by the square of height in meters) also did not differ significantly between the MoMHR and THA cohorts (26.9 ± 5.5 vs 28.9 ± 9.6, P = .35, Table 1 ). However, the male/female (M:F) ratio between the MoMHR and THA cohorts was significantly different (25:4 vs 8:14, P = .003, Table 1 ).
|Demographic Data||MoMHR (n = 29)||THA (n = 22)||P Value|
|Mean age (standard deviation [SD])||48.5 (8.7)||52.1 (12.6)||.22|
|Body mass index (SD)||26.9 (5.5)||28.9 (9.6)||.35|
A priori power analysis, based on a previous total joint pain study, indicated a required 13 patients per group at an α of 0.05, powered at 0.80. At an α of 0.05 and a power of 0.90, 17 patients per group would be required. Accounting for attrition, recruitment level was targeted at 19 patients per group, yielding a total n of 38 patients.
Enrolled patients strictly adhered to the standardized anesthesia and postoperative pain management protocol involving spinal regional anesthesia and a regimented non–patient-controlled methodology. Spinal medication included bupivacaine 0.75% in dextrose (8.25% spinal injection in sterile hyperbaric saline solution). Standardized postoperative pain management included ketorolac 30 mg intravenous piggyback (IVPB) every 6 hours, standing for 48 hours, and oxycodone immediate release 10 mg was offered every 4 hours for breakthrough pain. After surgery, pain and patient satisfaction were assessed via visual analog scale (VAS) at 3, 6, 24, and 48 hours with 24 hours as the primary end point. All patients participated twice a day in sessions with both physical and occupational therapists, starting on postoperative day 1. Patients were weight bearing as tolerated immediately after surgery and maintained posterior hip precautions. Estimated blood loss (EBL) and LOS data were also collected.
Data were collected by a blinded, third-party research assistant and stored within an encrypted Microsoft Excel (Microsoft Corp, Redmond, WA) spreadsheet. Blinded personnel also performed the data analysis using SPSS 18.0 (IBM Inc, Armonk, NY) to maximize removal of subjective bias in our final results. Categorical data were analyzed via Fisher exact test and continuous, ordinal data were analyzed via unpaired 2-tailed t -tests to compare the cohorts. Baseline confounding factors included in adjusted statistical analysis included age, gender, and BMI; these factors were controlled during cohort comparison, which was analyzed via multivariate analysis of covariance (MANCOVA). Level of significance was set to a P value of .05.
In addition to controlling for baseline confounding factors (age, gender, and BMI), incision length was also included as a confounding factor because it could have a potential impact on postoperative pain. Because the MoMHR cohort had a significantly larger incision length than the THA cohort (20.4 ± 4.3 cm vs 16.7 ± 6.1 cm, P = .014, Table 2 ), the significant difference was included as a confounding, controllable factor.