OBJECTIVEThe authors conducted a study to determine whether a change in T1 tilt results in a compensatory change in the cervical sagittal vertical axis (SVA) in a cadaveric spine model.METHODSSix fresh-frozen cadavers (occiput [C0]–T1) were cleaned of soft tissue and mounted on a customized test apparatus. A 5-kg mass was applied to simulate head weight. Infrared fiducials were used to track segmental motion. The occiput was constrained to maintain horizontal gaze, and the mounting platform was angled to change T1 tilt. The SVA was altered by translating the upper (occipital) platform in the anterior-posterior plane. Neutral SVA was defined by the lowest flexion-extension moment at T1 and recorded for each T1 tilt. Lordosis was measured at C0–C2, C2–7, and C0–C7.RESULTSNeutral SVA was positively correlated with T1 tilt in all specimens. After increasing T1 tilt by a mean of 8.3° ± 2.2°, neutral SVA increased by 27.3 ± 18.6 mm. When T1 tilt was reduced by 6.7° ± 1.4°, neutral SVA decreased by a mean of 26.1 ± 17.6 mm.When T1 tilt was increased, overall (C0–C7) lordosis at the neutral SVA increased from 23.1° ± 2.6° to 32.2° ± 4.4° (p < 0.01). When the T1 tilt decreased, C0–C7 lordosis at the neutral SVA decreased to 15.6° ± 3.1° (p < 0.01). C0–C2 lordosis increased from 12.9° ± 9.3° to 29.1° ± 5.0° with increased T1 tilt and decreased to −4.3° ± 6.8° with decreased T1 tilt (p = 0.047 and p = 0.041, respectively).CONCLUSIONSNeutral SVA is not a fixed property but, rather, is positively correlated with T1 tilt in all specimens. Overall lordosis and C0–C2 lordosis increased when T1 tilt was increased from baseline, and vice versa.

The optimal type of antibiotic spacer for the treatment of a knee periprosthetic joint infection (PJI) remains a topic of debate. Although the ultimate goal of an antibiotic spacer is infection control, contemporary spacer iterations, such as the use of a new femoral component (NFC), may offer unique advantages. The primary goal of this study was to compare rates of infection control and functional outcomes between contemporary spacer types. We retrospectively reviewed 96 patients who underwent removal of a total knee arthroplasty with insertion of an antibiotic spacer for knee PJI over a 14-year period at a single institution with a minimum 1-year follow-up. Three patient cohorts were defined based on spacer type: NFC (n=30), cement-on-cement (n=19), and static (n=47). There was no association between spacer type and the odds of infection clearance ( P =.60). The NFC spacers resulted in increased knee range of motion before replantation and improved ambulatory status at 8 weeks postre-plantation, although no difference was seen at final follow-up. The use of NFC spacers may provide functional advantages over their contemporary counterparts, and the potential of NFC spacers to be used in single-stage exchange arthroplasty remains an appealing area of investigation. Future high-powered, prospective, noninferiority studies between contemporary spacer types are needed. [ Orthopedics . 2022;45(2):109–115.]

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