64 patients were included in the final analysis. Five were excluded from the study: one patient was diagnosed with early periprosthetic join infection, there was one case of metal hypersensitivity and three patients were lost to follow up. There were 76,6% (49 pts) of females and 23,4% of males (15 pts) in study population and mean age was 67,6 yrs. (48–84, ± 7,42). Mean follow up time was 231,6 days (181–318, ± 34,3). 67,2% of patients were diagnosed with arterial hypertension, 26,6% suffered from circulatory diseases other than hypertension, whereas 18% were diagnosed with diabetes mellitus. 14% of patients had hypothyroidism and 1,5% suffered from epilepsy. There were no cases of ischemic stroke or depression in study cohort [Table 1].
Table 1
Demographics and comorbidities of the study population (with range and standard deviation in brackets where applicable).
Age, yrs | 67,6 (48–84, ± 7,42) |
Female | 76,7% |
Male | 23,3% |
Follow-up, days | 231,6 (181–318, ± 34,3) |
Hypertension | 67,2% |
Circulatory diseases (other than hypertension) | 26,6% |
Diabetes mellitus | 18% |
Hypothyroidism | 14% |
Epilepsy | 1,5% |
Ischemic stroke/TIA | 0 |
Depression | 0 |
After the follow up there were two groups of patients: group A (pain-free) comprised of 21 (33%) patients and group B (any pain), which consisted of 43 (67%) patients. There were no statistically significant differences in terms of age (69,9 ± 6,2 vs 66,5 ± 7,8, p = NS) or gender (females 76% vs 77%, p = NS, males 24% vs 23%, p = NS).
There were no statistically significant differences between groups A and B in respect of arterial hypertension (62% vs 69,8%, p = NS), circulatory diseases (28,6% vs 25,6%, p = NS), diabetes mellitus (14,3% vs 21%, p = NS), hypothyroidism (14,3% vs 14%, p = NS) and epilepsy (0% vs 2,3%, p = NS). In terms of preoperative VAS score [7 (4,5–9,5) vs 7 (3–10); p = NS], as well as total WOMAC score [57 (33–80) vs 58 (9–83) p = NS] no significant differences were observed. Duration of preoperative pain was significantly shorter in group A than in group B [36 mo. (12–180) vs 72 mo. (24–180), p = 0,011294]. Preoperative flexion (101,2 ± 13,3 deg vs 105 ± 13,2 deg, p = NS) and flexion contracture [10 deg (0–20) vs 10 deg (0–30), p = NS], as well as Ahlback grade [3 (1–5) vs 2 (1–5), p = NS] did not differ between study groups.
In KOOS subscale such as pain [44,0 (19,0–67,0) vs 42,0 (14,0–86,0), p = NS], other symptoms [39,0 (18,0–75,0) vs 36,0 (4,0-100,0), p = NS], activities of daily life [41,0 (9,0–72,0) vs 40,0 (12,0–90,0), p = NS] and quality of life (20,8 ± 14,8 vs 25,7 ± 13,5, p = NS) patients from group A and B had similar results.
No correlation was found between BDI score and postoperative pain intensity. No statistically significant differences between groups A and B was observed in terms of PPTs in the joint line [2,1(1,0–5,5) vs 2,5 (1,0–10,0), p = NS] and on the contralateral forearm [3,2(1,0–8,0) vs 3,2(1,5–7,2), p = NS]. Study groups were fairly similar in respect of radiological parameters of the operated knee [Table 2].
Table 2
Comparative analysis of preoperative parameters (in brackets range and standard deviation where applicable). Kgf – Kilogram-force
| Group A | Group B | p |
Age, yrs | 69,9 ± 6,2 | 66,5 ± 7,8 | NS |
Female | 76% | 77% | NS |
Male | 24% | 23% | NS |
Hypertension | 62% | 69,8% | NS |
Circulatory diseases | 28,6% | 25,6% | NS |
Diabetes mellitus | 14,3% | 21% | NS |
Hypothyroidism | 14,3% | 14% | NS |
Epilepsy | 0% | 2,3% | NS |
VAS | 7 (4,5–9,5) | 7 (3–10) | NS |
WOMAC | 57 (33–80) | 58 (9–83) | NS |
KOOS pain | 44,0 (19,0–67,0) | 42,0 (14,0–86,0) | NS |
KOOS other symptoms | 39,0 (18,0–75,0) | 36,0 (4,0-100,0) | NS |
KOOS activities of daily life | 41,0 (9,0–72,0) | 40,0 (12,0–90,0) | NS |
KOOS quality of life | 20,8 ± 14,8 | 25,7 ± 13,5 | NS |
Ahlback grade | 3 (1–5) | 2 (1–5) | NS |
PPTs knee, kgf | 2,1(1,0–5,5) | 2,5 (1,0–10,0) | NS |
PPTs forearm, kgf | 3,2(1,0–8,0) | 3,2(1,5–7,2) | NS |
Flexion, ° | 101,2 ± 13,3 | 105 ± 13,2 | NS |
Flexion contracture, ° | 10 (0–20) | 10 (0–30) | NS |
Pain duration, mo | 36 (12–180) | 72 (24–180) | 0,011294 |
6 months after the surgery patients were examined in terms of range of motion and no differences in flexion [100 deg (80–120) vs 110 deg (90–120), p = NS] and flexion contracture [0 deg (0–20) vs 0 deg (0–15), p = NS] were observed. No signs of loosening or periprosthetic fracture were found. In respect of KOOS subscales such as pain (88,1 ± 7,5 vs 63,2 ± 19,0, p < 0,0001), other symptoms (79,7 ± 11,2 vs 58,8 ± 16,8, p < 0,0001), activities of daily life (84,9 ± 11,6 vs 61,2 ± 18,5, p < 0,0001) and quality of life (68,3 ± 16,1 vs 46,8 ± 17,4, p < 0,0001) significant differences were observed, which was also seen in WOMAC total score (14,7 ± 9,0 vs 35,4 ± 16,0, p < 0,0001). PPTs were significantly higher in group A compared to group B both in the joint line [4,6 (2,5–8,0) vs 3,0(1,0–10,0), p = 0,000277] and on the contralateral forearm [5,5 (3,2–9,0) vs 3,6(1,0–10,0), p = 0,000675]. None of patients in group A described pain as severely limiting daily life compared to 25,6% of patients in group B confirming such limitations (p = 0,0149). Satisfaction rate in group A was 95,2% compared to 67,4% in group B (p = 0,03151). Logistic regression was performed for duration of preoperative pain and odds ratio was calculated. 1,27- fold increase in prevalence of chronic post-surgical pain with every 12 month of preoperative pain duration was found (p = 0,008779) [Table 3].
Table 3
Comparative analysis of postoperative parameters (in brackets range and standard deviation where applicable). Kgf – Kilogram-force
| Group A | Group B | p |
Flexion, ° | 100 (80–120) | 110 (90–120) | NS |
Flexion contracture, ° | 0 (0–20) | 0 (0–15) | NS |
KOOS pain | 88,1 ± 7,5 | 63,2 ± 19,0 | < 0,0001 |
KOOS other symptoms | 79,7 ± 11,2 | 58,8 ± 16,8 | < 0,0001 |
KOOS activities of daily life | 84,9 ± 11,6 | 61,2 ± 18,5 | < 0,0001 |
KOOS quality of life | 68,3 ± 16,1 | 46,8 ± 17,4 | < 0,0001 |
WOMAC | 14,7 ± 9,0 | 35,4 ± 16,0 | < 0,0001 |
PPTs knee, kgf | 4,6 (2,5–8,0) | 3,0(1,0–10,0) | 0,000277 |
PPTs forearm, kgf | 5,5 (3,2–9,0) | 3,6(1,0–10,0) | 0,000675 |
Severe limitation of daily life | 0% | 25,6% | 0,0149 |
Satisfaction | 95,2% | 67,4% | 0,03151 |