Introduction

            Surgery of the lumbar spine has been shown to alter the mechanics of the hip and knee joints, leading to osteoarthritis and eventually, joint arthroplasty. Minimally invasive spinal (MIS) surgery has been shown to lead to decreased complication rates and improved range of motion when compared to open spinal surgery. In this retrospective analysis, we examine the incidence of hip and knee pathology following MISS and open lumbar fusion.

Methods

            Using the PearlDiver Mariner database of insurance claims from Q32015 to 2018, patient receiving MIS or open lumbar fusion (single- and multi-level) were selected using ICD-10 procedural codes. MIS and open cohorts were matched based on age, sex, and comorbidities. Matched cohorts were followed longitudinally for the length of the database to determine rates of the following outcomes (first instance only): hip/knee pain, hip/knee osteoarthritis, total hip arthroplasty (THA) and total knee arthroplasty (TKA). The mean days to each outcome were also determined.

Results

            A total of 1923 patients received MISS lumbar fusion compared to 179,614 open fusions. The majority of patients from both cohorts were older than 65 (56% MIS and 56% open). The mean number of comorbidities was 2.6 for MIS and 2.5 for open. Length of stay was 3.1 days for MIS and 3.5 days for open. For single level fusions, 12% of MIS patients and 11% of open developed hip or knee osteoarthritis (p = 0.70); 3% of MIS and 4% of open received TKA (p= 0.69); 3% of MIS and 2% of open received THA (0.33). Mean time to hip or knee arthritis was 439 days for MIS and 460 days for open (p = 0.69). Mean time to TKA was 686 days for MIS and 565 days for open (p = 0.22). Mean time to THA was 382 days for MIS and 420 days for open (p = 0.69). For multi-level fusions, 14% of MIS patients and 11% of open developed hip or knee osteoarthritis (p = 0.14); 6% of MIS and 5% of open received TKA (p= 0.38); 3% of both MIS and open received THA (0.75). Mean time to hip or knee arthritis was 481 days for MIS and 532 days for open (p = 0.69). Mean time to TKA was 561 days for MIS and 502 days for open (p = 0.52). Mean time to THA was 471 days for MIS and 677 days for open (p = 0.11).

Discussion

            Rates of hip and knee pathology and arthroplasties following lumbar fusions were not significantly different between surgical techniques. MIS lumbar fusion may be considered an acceptable alternative to open procedures and, given the technique’s benefits of lower cost, decreased hospital stay, and fewer complications, may be superior to older open techniques. Future research can compare outcomes of MIS and open techniques for additional spinal surgeries and spinal levels.